Adaptive writing method for high-density optical recording apparatus and circuit thereof

ABSTRACT

An optical recording medium is provided, the optical recording medium including a plurality of zones configured to store data corresponding to an adaptive write pulse, the adaptive write pulse including a first pulse, a last pulse, and a multi-pulse train, the adaptive write pulse being different for each of the plurality of zones, the plurality of zones being reflected by a grouping table, the grouping table being configured to generate an adaptive write pulse waveform by varying a position of a rising edge of a first pulse of a mark to be written according to a length of the mark to be written and a leading space, the adaptive write pulse waveform being generated without regard for a trailing space of a present mark being written using the adaptive write pulse waveform, the adaptive write pulse being configured to correspond to the adaptive write pulse waveform, and store rising edge data of the first pulse of the adaptive write pulse waveform varying according to corresponding stored values of lengths of marks to be written. A width of the first pulse is varied by varying the position of the rising edge.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/122,912,filed on May 19, 2008, which is a continuation of application Ser. No.11/432,473, filed on May 12, 2006, now U.S. Pat. No. 7,391,698, which isa continuation of application Ser. No. 10/774,404, filed Feb. 10, 2004,now U.S. Pat. No. 7,209,423, which is a continuation of application Ser.No. 09/609,822, filed Jul. 3, 2000, now U.S. Pat. No. 7,158,461, whichis a divisional of application Ser. No. 09/359,128, filed Jul. 23, 1999,now U.S. Pat. No. 6,631,110 and claims the benefit of Korean PatentApplication No. 98-29732, filed Jul. 23, 1998, in the Korean IndustrialPatent Office, the entire disclosures of which are incorporated hereinby reference for all purposes.

BACKGROUND

1. Field of the Invention

The following description relates to an adaptive writing method for ahigh-density optical recording apparatus and a circuit thereof, and moreparticularly, to an adaptive writing method for optimizing light powerof a light source, e.g., a laser diode, to be suitable tocharacteristics of a recording apparatus, and a circuit thereof.

2. Description of the Related Art

With the multi-media era requiring high-capacity recording media,optical recording systems employing high-capacity recording media, suchas a magnetic optical disc drive (MODD) or a digital versatile discrandom access memory (DVD-RAM) drive, have been widely used.

As the recoding density increases, such optical recording systemsrequire optimal and high-precision states. In general, with an increasein recording density, temporal fluctuation (to be referred to as jitter,hereinafter) in a data domain increases. Thus, in order to attainhigh-density recording, it is very important to minimize the jitter.

Conventionally, a write pulse is formed as specified in the DVD-RAMformat book shown in FIG. 1B, with respect to input NRZI (Non-Return toZero Inversion) data having marks of 3T, 5T and 11T (T being the channelclock duration), as shown in FIG. 1A. Here, the NRZI data is dividedinto mark and space. The spaces are in an erase power level foroverwriting. The waveform of a write pulse for marks equal to or longerthan 3T mark, that is, 3T, 4T, . . . 11T and 14T is comprised of a firstpulse, a last pulse and a multi-pulse train. Here, only the number ofpulses in the multi-pulse train is varied depending on the magnitude ofa mark.

In other words, the waveform of the write pulse is comprised of acombination of read power (FIG. 1C), peak power or write power (FIG. 1D)and bias power or erase power (FIG. 1E). Here, the respective powersignals shown in FIGS. 1C, 1D and 1E are all low-active signals.

The waveform of the write pulse is the same as that in accordance withthe first generation 2.6 GB DVD-RAM standard. In other words, inaccordance with the 2.6 GB DVD-RAM standard, the waveform of the writepulse is comprised of a first pulse, a multi-pulse train and a lastpulse. Although the rising edge of the first pulse or the falling edgeof the last pulse can be read from a lead-in area to be used, adaptivewriting is not possible since the write pulse is fixed to be constant.

Therefore, when a write operation is performed by forming such a writepulse as shown in FIG. 1B, severe thermal interference may occur backand forth with respect to a mark in accordance with input NRZI data. Inother words, when a mark is long and a space is short or vice versa,jitter is most severe. This is a major cause of lowered systemperformance. Also, this does not make it possible for the system to beapplied to high-density DVD-RAMs, e.g., second generation 4.7 GBDVD-RAMs.

SUMMARY

In one general aspect, there is provided an optical recording medium,including a plurality of zones configured to store data corresponding toan adaptive write pulse, the adaptive write pulse including a firstpulse, a last pulse, and a multi-pulse train, the adaptive write pulsebeing different for each of the plurality of zones, the plurality ofzones being reflected by a grouping table, the grouping table beingconfigured to generate an adaptive write pulse waveform by varying aposition of a rising edge of a first pulse of a mark to be writtenaccording to a length of the mark to be written and a leading space, theadaptive write pulse waveform being generated without regard for atrailing space of a present mark being written using the adaptive writepulse waveform, the adaptive write pulse being configured to correspondto the adaptive write pulse waveform, and store rising edge data of thefirst pulse of the adaptive write pulse waveform varying according tocorresponding stored values of lengths of marks to be written. A widthof the first pulse is varied by varying the position of the rising edge.

The general aspect of the medium may further provide that the groupingtable is further configured to store the rising edge data of the firstpulse for the adaptive write pulse waveform according to correspondingstored values of lengths of marks to be written, and store the leadingspace grouped according to a first preset length of the mark and spaceand a second preset length of the mark and space.

The general aspect of the medium may further provide that pulse groupsof the grouping table include a short pulse group and an other pulsegroup.

In another general aspect, there is provided an optical recordingmedium, including a plurality of zones configured to store datacorresponding to an adaptive write pulse, the adaptive write pulseincluding a first pulse, a last pulse, and a multi-pulse train, theadaptive write pulse being different for each of the plurality of zones,the plurality of zones being reflected by a grouping table, the groupingtable having width data grouped in pulse groups that group first andlast pulses of a write pulse waveform by corresponding lengths of apresent mark of input data and a leading space of the present mark togenerate an adaptive write pulse waveform by varying a position of arising edge of the first pulse of a mark to be written according to alength of at least a mark to be written and/or a leading space, theadaptive write pulse being configured to correspond to the adaptivewrite pulse waveform, the grouping table being configured to storerising edge data of the first pulse of the write pulse waveform groupedin corresponding pulse groups according to lengths of marks to bewritten and lengths of spaces adjacent to the marks to be written. Thewidth of the first pulse is varied by varying the position of the risingedge.

In another general aspect, there is provided an optical recordingmedium, including a plurality of zones configured to store datacorresponding to an adaptive write pulse, the adaptive write pulseincluding a first pulse, a last pulse, and a multi-pulse train, theadaptive write pulse being different for each of the plurality of zones,the plurality of zones being reflected by a grouping table, the groupingtable being configured to generate an adaptive write pulse waveform byvarying a position of a rising edge of a first pulse of the mark to bewritten according to a length of at least a mark to be written and aleading space, the adaptive write pulse being configured to correspondto the adaptive write pulse waveform, and store rising edge data of thefirst pulse of the write pulse waveform grouped in corresponding pulsegroups according to lengths of marks to be written and lengths of spacesadjacent to the marks to be written. The width of the first pulse isvaried by varying the position of the rising edge.

The general aspect of the medium may further provide that the pulsegroups include a short pulse group and an other pulse group, and pulsesof the other pulse group have magnitudes that are greater thanmagnitudes of pulses of the short pulse group.

Other features and aspects may be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A through 1E are waveform diagrams illustrating examples ofconventional write pulses.

FIG. 2 is a block diagram illustrating an example of an adaptive writingcircuit for a high-density optical recording apparatus.

FIGS. 3A through 3G are waveform diagrams illustrating examples of anadaptive write pulse recorded by the adaptive writing circuit shown inFIG. 2.

FIG. 4 illustrates examples of grouping of input data.

FIG. 5 is a table illustrating an example of the combination of pulsesgenerated by the grouping shown in FIG. 4.

FIG. 6 is a table illustrating an example of rising edge shift values ofa first pulse.

FIG. 7 is a table illustrating an example of falling edge shift valuesof a last pulse.

FIG. 8 is a flowchart of an example of an adaptive writing method.

FIG. 9 is a graph of an example for comparing jitter generated by theadaptive writing method of FIG. 8 and the conventional writing method.

Throughout the drawings and the detailed description, unless otherwisedescribed, the same drawing reference numerals will be understood torefer to the same elements, features, and structures. The relative sizeand depiction of these elements may be exaggerated for clarity,illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. Accordingly, various changes,modifications, and equivalents of the systems, apparatuses and/ormethods described herein will be suggested to those of ordinary skill inthe art. Also, descriptions of well-known functions and constructionsmay be omitted for increased clarity and conciseness.

An adaptive writing circuit, as shown in FIG. 2, includes a datadiscriminator 102, a write waveform controller 104, a microcomputer 106,a write pulse generator 108 and a current driver 110. In other words,the data discriminator 102 discriminates input NRZI data. The writewaveform controller 104 corrects the waveform of a write pulse inaccordance with the discrimination result of the data discriminator 102and land/groove signal. The microcomputer 106 initializes the writewaveform controller 104 or controls the data stored in the writewaveform controller 104 to be updated in accordance with writeconditions. The write pulse generator 108 generates an adaptive writepulse in accordance with the output of the write waveform controller104. The current driver 110 converts the adaptive write pulse generatedfrom the write pulse generator 108 into a current signal in accordancewith the light power levels of the respective channels to drive a lightsource.

Next, the operation of the apparatus shown in FIG. 2 will be describedwith reference to FIGS. 3 through 7.

In FIG. 2, the data discriminator 102 discriminates the magnitude of amark corresponding to the present write pulse (to be referred to as apresent mark), the magnitude of the front-part space corresponding tothe first pulse of the present mark (to be referred to as a leadingspace, hereinafter) and the magnitude of the rear-part spacecorresponding to the last pulse of the present mark (to be referred toas a trailing space) from input NRZI data, and applies the magnitudes ofthe leading and trailing spaces and the magnitude of the present mark tothe write waveform controller 104.

Here, the magnitudes of the leading and trailing spaces and themagnitude of the present mark may range from 3T to 14T. There can bemore than 1,000 possible combinations. Thus, circuits or memories forobtaining the amounts of shift in rising edges of the first pulses andfalling edges of the last pulses are necessary with respect to allcases, which complicates the system and hardware. Therefore, themagnitudes of the present mark and the leading and trailing spaces ofinput NRZI data are grouped into a short pulse group, a middle pulsegroup and a long pulse group and the grouped magnitudes of the presentmark and the leading and trailing spaces are used.

The write waveform controller 104 shifts the rising edge of the firstpulse back and forth in accordance with the magnitudes of the leadingspace and the present mark, supplied from the data discriminator 102, orshifts the falling edge of the last pulse back and forth in accordancewith the magnitudes of the present mark and the trailing space, to thusform a write waveform having an optimal light power. Here, themulti-pulse train of a mark takes the same shape as shown in FIG. 3B,that is, 0.5T.

Also, the write waveform controller 104 can correct the rising edge ofthe first pulse of the present mark and the falling edge of the lastpulse of the present mark into different values in accordance withexternally applied land/groove signals (LAND/GROOVE) indicating whetherthe input NRZI data is in a land track or a groove track. This is forforming a write waveform in consideration of different optimal lightpowers depending on the land and groove. A difference of 1-2 mW in theoptimal light powers between the land and the groove, and may bespecifically set or managed by the specifications.

Therefore, the write waveform controller 104 may be constituted by amemory in which data corresponding to a shift value of the rising edgeof the first pulse and a shift value of the falling edge of the lastpulse in accordance with the magnitude of the present mark of input NRZIdata and the magnitudes of the leading and trailing spaces thereof, isstored, or a logic circuit. In the case that the write waveformcontroller 104 is constituted by a memory, the widths of the first pulseand the last pulse are determined as channel clocks (T) plus and minus adata value (shift value) stored in the memory. Also, in this memory,shift values of the first and last pulses of the mark for each of a landand a groove may be stored. A table in which the shift value of therising edge of the first pulse is stored and a table in which the shiftvalue of the falling edge of the last pulse is stored may beincorporated. Alternatively, as shown in FIGS. 6 and 7, two separatetables may be prepared.

A microcomputer 106 initializes the write waveform controller 104 orcontrols the shift values of the first and/or last pulse(s) to beupdated in accordance with recording conditions. In particular, inaccordance with zones, the light power can vary or the shift values ofthe first and last pulses can be reset.

The pulse width data for controlling the waveform of the write pulse isprovided to the write pulse generator 108. The write pulse generator 108generates an adaptive write pulse, as shown in FIG. 3F, in accordancewith the pulse width data for controlling the waveform of the writepulse supplied from the write waveform controller 104 and suppliescontrol signals shown in FIGS. 3C, 3D and 3E, for controlling thecurrent flow for the respective channels (i.e., read, peak and biaschannels) for the adaptive write pulse, to the current driver 110.

The current driver 110 converts the driving level of the light power ofthe respective channels (i.e., read, peak and bias channels) intocurrent for a control time corresponding to the control signal forcontrolling the current flow of the respective channels to allow thecurrent to flow through the laser diode so that an appropriate amount ofheat is applied to the recording medium by continuous ON-OFF operationsof the laser diode or a change in the amounts of light. Here, a recorddomain as shown in FIG. 3G is formed on the recording medium.

FIG. 3A shows input NRZI data, which is divided into mark and space.FIG. 3B shows a basic write waveform, in which the rising edge of thefirst pulse of the write pulse lags behind by 0.5T, compared to therising edge of the present mark. FIG. 3C shows the waveform of a readpower of the adaptive write pulse, FIG. 3D shows the waveform of a peakpower of the adaptive write pulse, and FIG. 3E shows the waveform of abias power of the adaptive write pulse. FIG. 3F shows the waveform ofthe adaptive write pulse. The rising edge of the first pulse of thewrite waveform of the adaptive write pulse may be shifted back and forthin accordance with a combination of the magnitude of the leading spaceand the magnitude of the present mark. An arbitrary power (here, a readpower or a write power) is applied during the period corresponding tothe shift. Likewise, the falling edge of the last pulse of the adaptivewrite pulse may be shifted back and forth in accordance with acombination of the magnitude of the present mark and the magnitude ofthe trailing space. Also, an arbitrary power (here, a read power or awrite power) is applied during the period corresponding to the shift.

Alternatively, the falling edge of the last pulse may be shifted backand forth in accordance with the magnitude of the present mark,regardless of the magnitude of the trailing space of the present mark.

Also, rather than shifting the rising edge of the first pulse and thefalling edge of the last pulse, the edge of any one pulse may beshifted. Also, in view of the direction of shift, shifting may beperformed back and forth, only forward or only backward.

FIG. 4 illustrates grouping of input NRZI data, showing two examples ofgrouping. In the first example, if a low grouping pointer is 3 and ahigh grouping pointer is 12, then the mark of a short pulse group is 3T,the marks of a middle pulse group are from 4T to 11T and the mark of along pulse group is 14T. In the second example, if a low groupingpointer is 4 and a high grouping pointer is 11, then the marks of ashort pulse group are 3T and 4T, the marks of a middle pulse group arefrom 5T to 10T and the marks of a long pulse group are 11T and 14T. Asdescribed above, since both the low grouping pointer and the highgrouping pointer are used, utility efficiency is enhanced. Also,grouping can be performed differently for the respective zones.

FIG. 5 illustrates the number of cases depending on combinations ofleading and trailing spaces and present marks, in the case ofclassifying input NRZI data into three groups, as shown in FIG. 4, usinggrouping pointers. FIG. 6 illustrates a table showing shift values ofrising edges of the first pulse depending on the magnitude of theleading space and the magnitude of the present mark. FIG. 7 illustratesa table showing shift values of falling edges of the last pulsedepending on the magnitude of the present mark and the magnitude of thetrailing space.

FIG. 8 is a flow chart illustrating an embodiment of an adaptive writingmethod. First, a write mode is set (step S101). If the write mode isset, it is determined whether it is an adaptive writing mode or not(step S102). If it is determined in step S102 that the write mode is anadaptive write mode, a grouping pointer is set (step S103). Then, agrouping table depending on the set grouping pointer is selected (stepS104). The selected grouping table may be a table reflecting land/grooveas well as the grouping pointer. Also, the selected grouping table maybe a table reflecting zones of the recording medium.

Shift values of the rising edge of the first pulse are read from thetable shown in FIG. 6 in accordance with a combination of the presentmark and the leading space (step S105), and shift values of the fallingedge of the last pulse are read from the table shown in FIG. 7 inaccordance with a combination of the present mark and the trailing space(step S106).

The adaptive write pulse in which the first pulse and the last pulse arecontrolled in accordance with the read shift value is generated (stepS107). Then, the light powers of the respective channels for thegenerated adaptive write pulse, i.e., read, peak and bias powers, arecontrolled to drive a laser diode (step S108) to then perform a writeoperation on a disc (step S109). If the write mode is not an adaptivewrite mode, a general write pulse is generated in step S107.

FIG. 9 is a graph for comparing jitter generated by the adaptive writingmethod according to FIG. 8 and the conventional writing method. It isunderstood that, assuming that the peak light is 9.5 mW, the bottompower of a multi-pulse train is 1.2 mW, the cooling power is 1.2 mW andthe bias power is 5.2 mW, there is less jitter generated when writingthe adaptive write pulse according to FIG. 8 than when generated writingthe fixed write pulse according to the conventional writing method. Theinitialization conditions are a speed of 4.2 m/s, an erase power of 7.2mW and 100 write operations.

In other words, according to the examples described above, in adaptivelyvarying the marks of a write pulse, the rising edge of the first pulseis adaptively shifted in accordance with the magnitude of the leadingspace and the magnitude of the present mark of input NRZI data to thuscontrol the waveform of the write pulse, and/or the falling edge of thelast pulse is adaptively shifted in accordance with the magnitude of thepresent mark and the magnitude of the trailing space of input NRZI datato thus control the waveform of the write pulse, thereby minimizingjitter. Also, the waveform of the write pulse may be optimized inaccordance with land/groove signals. Also, in the examples describedabove, grouping may be performed differently for the respective zones,using grouping pointers.

A new adaptive writing method according to the examples described abovecan be adopted to most high-density optical recording apparatuses usingan adaptive writing pulse.

As described above, the widths of the first and/or last pulses of awrite pulse waveform are varied in accordance with the magnitude of thepresent mark of input NRZI data and the magnitude of the leading ortrailing space, thereby minimizing jitter to enhance system reliabilityand performance. Also, the width of a write pulse is controlled bygrouping the magnitude of the present mark and the magnitude of theleading or trailing spaces, thereby reducing the size of a hardware.

According to the examples described above, an adaptive writing method ofa write pulse generated in accordance with the magnitude of the presentmark of input data and the magnitudes of the leading and/or trailingspaces thereof may be provided. Further, according to the examplesdescribed above, an adaptive writing circuit for a high-density opticalrecording apparatus may be provided for optimizing light power of alaser diode by generating an adaptive write pulse in accordance with themagnitude of the present mark of input data and the magnitudes of theleading and trailing spaces thereof.

A number of examples have been described above. Nevertheless, it will beunderstood that various modifications may be made. For example, suitableresults may be achieved if the described techniques are performed in adifferent order and/or if components in a described system,architecture, device, or circuit are combined in a different mannerand/or replaced or supplemented by other components or theirequivalents. Accordingly, other implementations are within the scope ofthe following claims.

1. An optical recording medium, comprising: a data area comprising aplurality of zones; and a grouping table configured to store dataconfigured to calculate a width of a write pulse, and information on aposition of a falling edge data of a last pulse of an adaptive writepulse waveform based on a combination of a mark pulse groupcorresponding to a magnitude of a present mark to be written and a spacepulse group corresponding to a magnitude of a trailing space of thepresent mark.
 2. The optical recording medium of claim 1, wherein thegrouping table is further configured to store the falling edge data ofthe last pulse of the adaptive write pulse waveform and the trailingspace, the falling edge data being stored according to correspondingstored values of lengths of marks to be written, the stored trailingspace being grouped according to a last preset length of the mark andspace and a second preset length of the mark and space.
 3. The opticalrecording medium of claim 2, wherein pulse groups of the grouping tablecomprise a short pulse group and an other pulse group.
 4. An apparatusconfigured to write input data on an optical recording medium comprisinga data area and a grouping table, the grouping table comprisinginformation on a position of a falling edge of a last pulse based on acombination of a mark pulse group corresponding to a magnitude of apresent mark to be written and a space pulse group corresponding to amagnitude of a trailing space of the present mark, the apparatuscomprising: a discriminator configured to discriminate the mark pulsegroup and the space pulse group; a write waveform controller configuredto select the information on the position of the falling edge of thelast pulse from the grouping table based on the discriminated mark pulsegroup and the discriminated space pulse group, and generate an adaptivewrite pulse waveform based on the selected information on the positionof the falling edge of the last pulse; and a processor configured toprocess the input data on the optical recording medium based on theadaptive write pulse waveform.